Medical ablation systems (e.g., cryoablation systems, radio-frequency ablation systems, or the like) have proven therapeutic. Cryoablation systems can be used to form cold-induced lesions on patient tissue. Cryoablation systems have been used to reduce, or even eliminate, undesired electrical activity between adjacent cardiac tissues of the heart (arrhythmias). Radio frequency ablation systems (“RF ablation systems”) use microwave energy to form heat-induced lesions on patient tissue and can also be used to treat some of the same conditions as cryoablation systems, including arrhythmias.
One common type of arrhythmia, atrial fibrillation, is a result of abnormal electrical signals interfering with the normal electrical signal propagation along the tissues of the heart. Atrial fibrillation often originates near the ostia of the pulmonary veins. Mapping catheters can be used to locate the abnormal electrical signals and medical ablation systems (“ablation systems”) can be used to form lesions on patient tissue through which the abnormal electrical signals are propagated (e.g., tissue along the inner walls of the ostia (where the pulmonary veins open into the left atrium of the heart), or in proximity to the ostia). The cold-induced (or heat-induced) lesions can effectively block the initiation or propagation of the abnormal electrical signals, thereby preventing the abnormal electrical signals from interfering with the normal electrical signal propagation along the tissues of the heart.